linux-kernel - [PATCH v3 6/6] usb: gadget: uvc: allow ioctl to send response in status stage

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Message-Id: <20181219092647.12397-7-paul.elder@ideasonboard.com>
Date:   Wed, 19 Dec 2018 04:26:47 -0500
From:   Paul Elder <paul.elder@...asonboard.com>
To:     laurent.pinchart@...asonboard.com, kieran.bingham@...asonboard.com
Cc:     Paul Elder <paul.elder@...asonboard.com>, b-liu@...com,
        stern@...land.harvard.edu, rogerq@...com, balbi@...nel.org,
        gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v3 6/6] usb: gadget: uvc: allow ioctl to send response in status stage

We now have a mechanism to signal the UDC driver to reply to a control
OUT request with STALL or ACK, and we have packaged the setup stage data
and the data stage data of a control OUT request into a single
UVC_EVENT_DATA for userspace to consume. The ioctl UVCIOC_SEND_RESPONSE
in the case of a control OUT request sends a response to the data stage,
and so the ioctl now notifies the UDC driver to reply with STALL or ACK.
In the case of a control IN request, the ioctl sends the UVC data as
before.

Also tell the UDC to delay the status stage for this to work.

Signed-off-by: Paul Elder <paul.elder@...asonboard.com>
---
Changes from v2:
- calling usb_ep_set_halt in uvc_send_response if data->length < 0 is
  now common for both IN and OUT transfers so make that check common
- remove now unnecessary field setting for the usb_request to be queued
  for the status stage

Changes from v1:
- remove usb_ep_delay_status call from the old proposed API
- changed portions of uvc_send_response to match v2 API
- remove UDC warning that send_response is not implemented

 drivers/usb/gadget/function/f_uvc.c    |  4 ++--
 drivers/usb/gadget/function/uvc_v4l2.c | 23 +++++++++++++++++------
 2 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/drivers/usb/gadget/function/f_uvc.c b/drivers/usb/gadget/function/f_uvc.c
index d08957124e42..91388bb647e0 100644
--- a/drivers/usb/gadget/function/f_uvc.c
+++ b/drivers/usb/gadget/function/f_uvc.c
@@ -209,14 +209,13 @@ uvc_function_ep0_complete(struct usb_ep *ep, struct usb_request *req)
 	struct uvc_event *uvc_event = (void *)&v4l2_event.u.data;
 
 	if (uvc->event_setup_out) {
-		uvc->event_setup_out = 0;
-
 		memset(&v4l2_event, 0, sizeof(v4l2_event));
 		v4l2_event.type = UVC_EVENT_DATA;
 		uvc_event->data.length = req->actual;
 		memcpy(&uvc_event->data.data, req->buf, req->actual);
 		memcpy(&uvc_event->data.setup, &uvc->control_setup,
 		       sizeof(uvc_event->data.setup));
+
 		v4l2_event_queue(&uvc->vdev, &v4l2_event);
 	}
 }
@@ -251,6 +250,7 @@ uvc_function_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
 		 */
 		req->length = uvc->event_length;
 		req->zero = 0;
+		req->explicit_status = 1;
 		usb_ep_queue(f->config->cdev->gadget->ep0, req, GFP_KERNEL);
 	} else {
 		struct v4l2_event v4l2_event;
diff --git a/drivers/usb/gadget/function/uvc_v4l2.c b/drivers/usb/gadget/function/uvc_v4l2.c
index 35353ffdf3b4..0d4993144ab8 100644
--- a/drivers/usb/gadget/function/uvc_v4l2.c
+++ b/drivers/usb/gadget/function/uvc_v4l2.c
@@ -35,15 +35,26 @@ uvc_send_response(struct uvc_device *uvc, struct uvc_request_data *data)
 	struct usb_composite_dev *cdev = uvc->func.config->cdev;
 	struct usb_request *req = uvc->control_req;
 
+	if (data->length < 0)
+		return usb_ep_set_halt(cdev->gadget->ep0);
+
 	/*
 	 * For control OUT transfers the request has been enqueued synchronously
-	 * by the setup handler, there's nothing to be done here.
+	 * by the setup handler, we just need to tell the UDC whether to ACK or
+	 * STALL the control transfer.
 	 */
-	if (uvc->event_setup_out)
-		return 0;
-
-	if (data->length < 0)
-		return usb_ep_set_halt(cdev->gadget->ep0);
+	if (uvc->event_setup_out) {
+		/*
+		 * The length field carries the control request status.
+		 * Negative values signal a STALL and zero values an ACK.
+		 * Positive values are not valid as there is no data to send
+		 * back in the status stage.
+		 */
+		if (data->length > 0)
+			return -EINVAL;
+
+		return usb_ep_queue(cdev->gadget->ep0, req, GFP_KERNEL);
+	}
 
 	req->length = min_t(unsigned int, uvc->event_length, data->length);
 	req->zero = data->length < uvc->event_length;
-- 
2.19.2